These terms are shortened versions of the more proper anno aetatis suae, "In the year of his/her age.". Frequently found abbreviated on old tombstones, it appears variously as A.A.S., A.S., and most commonly aet; for example, if someone died in his 41st year, the marker might read "d. aet.41" or "ob. aet. 41". See obiit (a death list or an inscription found on tombstones) for further explanations.
A reference to youth.